Dispersion mill



Maw. 29, 1932. R TR VIS 1,851,071

DISPERSION MILL Filed Ju1'1e so. 1928 s Sheet s-Sheet 1 wvENToR Pl EHCEMASON TRAVIS March 29, 1932. p M R v s 1,851,071

DISPERSION MILL 7 Filed June 30. 1928 3 Sheets-Sheet 2 lNVENTOR PiERCEMASON TRAVIS March 29, 1932. p, TRAVIS DISPERSION MILL s Sheets-Sfieet sFiledJune 30; 1928 INVENTOR Pl ERCE MASON TRAVIS ATTORNEY Patented Mar.29, 1932 PATENT OFFICE EIERCE MASON TRAVIS, OF RIDGEWOOD, NEW JERSEYDISPERSION MILL Application filed Iune 30,

This invention relates to high-speed mechanical dispersion mills of theso-called colloid type, wherein the material to be treated is subjected,while in a liquid vehicle,

to an intensive dispersing action for the purpose of securing finecomminution, defiocculation, colloidal dispersion, emulsification,homogenization, the acceleration of chemical reaction or the like.

The operation of dispersion, or so-called colloid mills is based uponthe intense disruptive and dispersive forces set up in a liquid, whenconfined between closely adjacent, non-contacting surfaces relativelymoving at very high speeds. The most effective type of mill embodiesconcentric surfaces of revolution, and in its best known form comprisesa frusto-conical rotor surface surrounded by a frusto-conical statorsurface. This concentric cone arrangement serves to retain the materialsin an intervening gapor zone of action better than other types, andfacilitates fine adj ustment of the minute clearance between thesurfaces.

In the operation of the mill, the liquid material may be fed either atthe small or ta ered end of the cones or at the large end. f thematerial is fed at the small end, it will be drawn through the gap bythe inherent action of the mill itself, due to the acceleration impartedto the material by the centrifugal force, which progressively increasesfrom the small to the large end of the rotating cone. If the material isfed at the large end of the cones, pressure feeding must be utilized inorder to force the material through the gap against the action of thecentrifugal force which tends to expel it at the large end of the cone.

Due to the power-saving and larger operating capacity provided thereby,it is much more preferable to utilize feeding at the small end. However,where such manner of feed,- ing is used with present constructions,there is a tendency under various circumstances, for example where theconical slope is pronounced, for the material to be drawn through theWorking gap too quickly. As a consequence, the continuity of the streamof 50 material may be broken and the material 19213. Serial No. 289,448.

passed through the greaterpart of the gap in the form of detachedparticles and too rapidly for proper treatment.

It is an object of my invention to overcome the deficiencies of theprior practice and to provide an improved dispersion mill whereinfeeding at the small end is utilized with its inherent advantages, butwith the provision of means for avoiding the undesirable effects ofunduly accelerated passage of the mate- G0 rial through the mill.

The manner in which I accomplish the same is described in the followingspecification, taken in conjunction with the accompanying drawings, inwhich, %ig. 1 is a perspective view of the complete m1 Fig. 2 is alongitudinal vertical mid-section of the same;

Fig. 3 is an enlarged longitudinal view of one type of rotor that may beused therein;

Fig. 4 is a similar view of another type of rotor;

, Fig. 5 is an end view of the larger end of the rotor shown in Fig. 4;

I Fig. 6 is a cross-sectional view'of an impeller groove;

Fig. 7 is a similar view of a slightlymodified form of the same;

Fig. 8 is a cross-section of a further modi s0 fication.

Fig. 9 is an enlarged cross-section of a modified form of stator, and

Fig. 10 is a longitudinal mid-section on a reduced scale of a form ofrotor constructed for temperature control.

Referring to the drawings, and in particular to Figs. 1 and 2, referencenumeral 11 designates a stator member comprising a shell 12 and a liner13, which defines an elongated so chamber 14 of frusto-conical form. Atits smaller terminal, chamber 14 communicates With a feed chamber 15 andinlet 16, and at its larger terminal, with a discharge chamber 17 andoutlet 18 formed in a detachable shell 95 head 19. A detachable shellhead 21 covers the opposite end of the shell, and both the stator 11 andshell head 19 are provided with jackets 22 and 23, respectively, for thecirculation of a temperature regulating medium. 106

A rotor 24 of a frusto-com'cal form similar to that of the chamber 14 ismounted for rotation therein in closely adjacent, non-contacting,eo-axial relation, the surfaces 25 of the rotor and 26 of the statordefining a narrow working gap or clearance 27, shown in enlargedproportion for clarity, through which the materials to be dispersed arepassed.

Conical projections 28 and 29 of greater slope than the rotor proper,extend from the larger and smaller terminals thereof, respectively, forthe purposes to be described hereinafter, and these projections may beformed integrally with the rotor proper or detachably secured thereto.

Rotation of the rotor and its accompanying projections is accomplishedthrough the medium of a driving shaft 31, carried in bearings 32 and 33,which is connected directly with an electric motor 34 by means of aflexible coupling 35 of any suitable type. Packing glands 36 and 37 areprovided about the shaft 31, adjacentjhe bores in the respective shellheads 19 and 21, to secure proper sealing of the interior of the mill.

As will be noted from an inspection of Fig. 2, the bearing 32 isconstructed to permlt longitudinal adjustment of the rotor 24, to varythe clearance between the working surfaces 25 and 26 of the rotor andstator. TlllS bearing comprises a split, babbitt-lined bearing block 38provided with complementary semi-circular recesses in its removable cap39 and base 41 respectively, which receive circumferential projectionson the rotor shaft 31.

The block 38 is mounted to slide longitudinally in a channel 42, andcarries an integral nut 43 which projects through a longitudinal slot 44in the base of the channel. This nut engages an adjusting screw 45mounted in bearing lugs 46 and 47, and by means of fixed collars 48 and49 which-abut the bearing lugs, longitudinal movement of the screw isprevented and rotation thereof is translated into longitudinalmovement'of the bearing block and rotor. The screw 45 is actuated by ahand-wheel 51 which carries an indicator 52,

and by proper calibration of a stationary scale 53, determinateadjustment of the clearance in the mill may be readily obtained.

The rotor and stator may be either of the smooth-surfaced type 54, shownin Fig. 3, or of the roughened-surfaced type 24, shown in Figs. 2, 4 and5. This roughened surface is constituted of generally longitudinalchannels 56 preferably having rounded base corners, alternating withgenerally longitudinal flat faced teeth 57 and a similar surfaceconstruction is provided on the surroundin stator. Where a generallyapplicable and particularly effective construction is de ired. theroughened surface construction is best used. As will be noted from thedrawings. the rotor has the form of an elongated frustum of a cone ofmoderate slope. I have found quite suitable, for example, afrustoconical rotor having the slope of a cone whose apical angle isapproximately 1618.

Heretofore, rotors have taken the form of disc-like frustums, either ofpronounced slope or of very slight slope. In the first case, while rapidpassage of the material over the short dispersion surface results, theeffectiveness of treatment suffers accordingly. In the second case, thespeed of passage is greatly decelerated, but the advantages of highcapacity operation and power efiiciency are lost thereby,and with theshort dispersion surface, the resulting treatment still lacks thedesired increase in effectiveness. By using an elongated rotor ofmoderate slope, as in my construction, these deficiencies are supplied,and a reasonably rapid acceleration is obtained over a dispersionsurface sufficiently prolonged to assure very effective treatment.

The stator which surrounds the rotor in coaxial relationship therewithis preferably of like conical form.

In Figs. 3, 4 and 5 I have shown a construction for the dischargeterminal of the rotor, which substantially remedies the practicaldeficiencies heretofore accompanying smallend feeding.

This construction comprises impeller grooves 55 formed in the surface ofthe projection 28, which extend radially thereof to spaced points in thesurface of the rotor. In the smooth-surfaced rotor 54, Fig. 3, thegrooves terminate flush with the rotor surface, while in therough-surfaced rotor 24, Fig. 4 and 5, I have found the action to bemost effective when the grooves terminate in the channels 56, betweenthe longitudinal teeth 57 on the rotor. These grooves are preferably ofrectangular cross-section, as shown in Fig. 6, but may if desired be ofthe cross-sections shown in Figs. 7 and 8. The essential element of theconfiguration is that an obstructing face of the groove should beallgned in the direction of movement of the surface 28, either at rightangles itheretoas at 58 in Fig. 6, or 59 in Fig. 7, or at an acute anglethereto as at 61 in Fig. 8, in order that the liquid will not flow outof the groove until it reaches the terminus :thereof.

By increasing ordecreasing the number of grooves the retarding effectupon the discharge of the material from the working gap may berespectively intensified or diminlshed, and if a particularly Wide rangeof retardation is desired, it may be provided for by initially formingthe maximum number of grooves, and then inserting fillers, which may bescrewed or otherwise detachably affixed in the grooves, as the occasiondemands. Such contingency may also be anticipated by providing a seriesof detachable pro ections 28, each having a different number of grooves.The more pronounced the rotor slope the greater the number ofgroovesnecessary to maintain'a uniform retardation.

A conical projection 29 of less pronounced slope than projection 28, isdisposed at the smaller terminal of the rotor, to facilitateintroduction of the materials into the working gap 27, and thisprojection may be provided likewise with impeller grooves 62 of the samenature as those on the projections 28, to promote feeding.

In Fig. 9 I have shown a modified form of the unitary stator 11. Thissplit stator 63 is constructed to permit ready access to the interior ofthe mill for cleaning or other purposes. It comprises complementarysections 64 and 65 hinged together as at 66, either at the base, side ortop, which are provided diametrically opposite the hinge, with abuttingflanges 67, 68 adapted to be bolted, screwed, or otherwise detachablysecured together. To provide for this separable relationship thecircumferential stator jacket'is divided into two semi-circumferentialsections 69, 70 having individual inlets and outlets.

Fig. 10 shows a rotor construction adapted for internal circulation of atemperature,

regulating medium. This rotor comprises a hollow shell 71 shrunk on theends of stub shafts 72 and 73. Shaft 72 is provided with a central bore7 4 which accommodates an inlet pipe 75, and shaft 73 carries at its enda hollow cylindrical bracket '76 which sulpports the projecting terminalof pipe 75. T e wal 77 of the bracket 73 is provided with a number ofelongated slots 83 for the passage of the fluid from pipe 75.

Shaft 72 is mounted at its recessed portion 78 in a suitably alteredbearing of the general type shown at 32 Fig. 2, and has its terminalportion 79 rotatably mounted in a coupling 80. The coupling 80 comprisesan inlet chamber 81 communicating with pipe 75, and an outlet chamber 82communicating with the discharge passage 7 4, through which con duitscold water, steam, or other suitable temperature regulating medium iscirculated through the rotor.

This rotor construction is particularly advantageous where cooling ofthe working gap is contemplated. Upon rotation the hollow rotor will actin the same fashion as a centrifugal separator, and the coolest and mostdense liquid inside the shell will tend tobe maintained in contact withthe inner peripheral surface thereof.

The operation of the mi as follows:

The roughened working surfaces 25 and 26 of the rotor and stator, arefirst spaced to the desired degree by adjustment of the bear ing 32. Theeffective clearance is relatively slight and is best maintained betweenvery 11 is substantiallynarrow. limits, depending upon the degree ofdispersion desired and the peripheral speed of the rotor.

For the fine dispersion of most materials at the high peripheral speedsordinarily used, a clearance ranging between .002-.O10 inches is veryeffective, although for some materials this upper limit may be exceededwith good results. At particularly high peripheral speeds, the clearancefor fine dispersion may appreciably exceed .010 inches, the specificvariance being dependent upon the speed attained and the nature of thematerial involved. Where a course dispersion provides the material in asatisfactory form, the clearance may be altered as the circumstancesdictate.

The rotor is then brought up to a peripheral speed suitable fordispersion, which rarely is less than 3000 ft. min. and ordinarilyranges in the vicinity of 5000 ft. min. and higher. Due to theparticular constructional arrangement of my device, I can utilize arotor of such large diameter that the requisite fore, permits the use ofheavy motors of commonly available design, operating at the usualcommercial speeds or R. P. M. and facilitates increasing the mill outputappreciably.

The material to be introduced into the mill should be provided in liquidform, for in the operation of a true dispersion mill, as distinguishedfrom the old grindingmill, it is essential that an appreciable amount ofliquid be present, in order that dispersion, may be accomplished betweenthe non-contacting working surfaces. Where solids are being dispersed, aslurry of the same in a suitable liquid medium is first formed. Inemulsification and similar liquid contact, the liquidsthemselvesgenerally furnish a satisfactory medium. Where plastics areconcerned the addition of or conversion to a more liquid medium dependsupon the degree of plasticity which the mill will conveniently handle aswell as the nature of the dispersion desired.

When a properly liquid material has been prepared, it is continuouslyintroduced through inlet 16 into feed chamber 14 (Fig. 2%, whence it isdrawn into the working gap 2 and in the event projection 29 is utilized,with the added accelerative action of that grooved projection.

In its passage through the gap, the material is subjected to a terrificdisruptive action, of much greater intensity and of different type inthe rough surface mill than in the smooth, which results in thoroughdispersion or deflocculation of the aggregated particles.

When materials which are sensitive to heat are being dispersed, it isdesirable to pass a suitable cooling medium through the stator and shellhead jackets 22 and 23, and if a considerable cooling efiect isnecessary, a water cooled rotor of the type shown in Fig. 10 may be usedin addition. If heat is desired in the dispersing action, a circulationof steam or other suitable heating medium may be provided.

The conformation of the working gap 27 is such that properly prolongedtreatment is afiorded with suitable axial acceleration of passage. Itis, however, by the action of the impeller groove construction at thedischarge terminal of my rotor that the deficiencies of the priorpractice are most markedly remedied. The exact nature of its action isdiflicult to predict accurately, but it suflices that I it results in aconsiderable increase in the effectiveness of the dispersing action,without unduly prolonged or impractically applied retardation. As notedhereinbefore, the number of grooves may be increased or decreased tovary the degree of retardation of discharge of the material.

The dispersed material in the discharge chamber 17 is pumped through theoutlet 18 by the pressure in the mill, but this action may besupplemented by a suitable pump connected to the discharge outlet.

I claim as my invention:

1. An apparatus for treating liquid material which comprises a conicalrotor adapted for rotation at high velocity, a conical statorsurrounding said rotor in closely adjacent, non-contacting relation,means for supplying liquid material to the smaller terminal of the gapbetween said rotor and stator, and rotatable impeller faces connectedwith said rotor and disposed radially of said rotor at the larger endthereof for retarding the discharge of material from said gap.

2. An apparatus for treating liquid material which comprises a conicalrotor adapted for rotation at high velocity, a conical statorsurrounding said rotor in closely adj acent, non-contact ng co-axialrelation, means for supplying liquid material to the smaller terminal ofthe gap between said rotor and stator. and impeller grooves disposed forrotation at the larger end of said rotor whereby the discharge ofmaterial from said gap is retarded.

3. In an apparatus for treating liquid material, the combination whichcompr ses a conical rotor adapted for rotation at high velocity, aconical stator surrounding said rotor in closely adjacent,non-contacting coaxial relation, means for feeding the liquid materialat the smaller terminal of said rotor and a rotatable con cal impellersurface mounted in co-axial relation with'said rotor at the largerterminal thereof for rotation therewith and having its base facing saidterminal of the rotor, whereby, upon rotation. said surface will set upmotion in the liquid in opposition to the flow of liquid induced by therotor.

4. In an apparatus for treating liquid material, the combination whichcomprises a conical rotor, a conical stator surrounding said rotor inclosely adjacent, non-contacting co-axial relation, means for feedingthe liquid material at the smaller terminal of said rotor and arotatable conical impeller surface of greater slope than said rotordisposed in coaxial but oppositely sloping relation to said rotor andhaving its base facing the larger terminal face of said rotor, saidsurface being rotatable with said rotor whereby, upon rotation, saidsurface will set up motion in the liquid in opposition to the flow ofliquid induced by the rotor.

5. In an apparatus for treating liquid material, the comb nation whichcomprises, a conical rotor, adapted to be rotated at high peripheralspeed, a conical stator surrounding, said rotor in closely adjacent,non-contacting concentric relation, and co-axial conical impellersurface projecting from the larger terminal of said rotor, said surfacebeing provided with radially disposed impeller faces.

6. In an apparatus for treating liquid material, the combination whichcomprises a conical rotor, a conical stator surrounding said rotor inclosely adjacent, non-contacting co-axial relation, and a co-axialconical impeller surface integral with the larger terminal of said rotorand having radially disposed impeller faces terminating at the surfaceof said rotor.

7. An apparatus for dispersing material, which comprises a conical rotoradapted for rotating at high velocity, a conical stator enclosing saidrotor in closely adjacent, noncontacting relation, said rotor and saidstator having their. opposing surfaces provided with longitudinallyextending alternate channels and teeth, and a conical impeller surfacerotatably disposed at the larger terminal of said rotor and havingradially extend ng grooves terminating directly in the channels of saidrotor surface.

8. An apparatus for dispersing material, which comprises afrusto-conical rotor adapted for rotation at high velocity, afrusto-conical stator surrounding said rotor in closely adjacent,non-contacting relation, said rotor and said stator having theiropposing surfaces provided with alternate longitudinal channels andteeth, and a conical surface rotatable with said rotor extending fromthe larger terminal thereof, said surface having radially extendingimpeller grooves terminating in the channels of said rotor surface,whereby discharge of material from the gap between said rotor and statoris retarded.

9. In an apparatus for treating liquid ma- .terials the combinationwhich comprises, a.

conical rotor adapted for rotation at high velocity, a. conical statorsurrounding said rotor in closely adjacent, noncontacting, coaxialrelation defining with said rotor a narrow intervening working gap thruwhich the liquid material is passed, means for supplying the liquidmaterial to the smaller terminal of said gap whence it will tend to bedrawn therethru by the centrifugal pumping action set up upon rotationof the rotor, and rotatable means for exerting a fluid pressure varyingwith the speed of rotation in opposition to the flow produced by saidpumping action to retard the discharge of said liquid material from thegap, the speed of rotation of said last named means being automaticallyincreased or decreased respectively as the rotor speed increases ordecreases.

10. In an apparatus for treating liquid material the combination whichcomprises, a

conical rotor adapted for rctation at high velocity, a casing membercompletely enclosingsaid rotor member and comprising a conical statormember disposed in concentric relationship to said rotor member definingtherewith a narrow intervening gap, said casing having a feed chamber atthe smaller end of said rotor and a discharge chamber at the larger endof said rotor, and a member rotatable with said rotor and disposed insaid discharge chamber for creating a centrifugal fluid back pressure toretard the discharge of liquid material from the gap between said rotorand stator.

In testimony whereof I aflix my signature.

' PIERCE MASON TRAVIS.

